Preparation of tetrakis(2,6-dimethylphenylisocyanide)cobalt(II) perchlorate in novel reactions

Abstract

Paramagnetic tetrakis(2,6-dimethylphenyliso- cyanide)cobalt(II) perchlorate, [Co(CNR) 4](ClO 4) 2, R  2,6-Me 2C 6H 3, has been prepared from pentakis- (2,6-dimethylphenylisocyanide)cobalt(II) perchlorate hemihydrate, [Co(CNR) 5](ClO 4) 2·0.5H 2O, in novel reactions with triphenylarsine and triphenylstibine. Analogous reaction with [Co(CNR) 5](BF 4) 2·0.5H 2O produced only [Co(CNR) 5]BF 4. Both [Co(CNR) 5]- X 2·0.5H 2O, X  ClO 4 −, BF 4 −, can be recrystallized from CH 2Cl 2, CHCl 3 or CH 2ClCH 2Cl in 0.15–0.30 M initial concentration, to produce [Co(CNR) 5]X 2·S (S  adducted solvent) in good yield. Recrystallization of [Co(CNR) 5](ClO 4) 2·0.5H 2O from dilute (C M ⩽ 5 X 10 −3 M) solution, however, produces [Co(CNR) 4](ClO 4) 2·S, while [Co(CNR) 5](BF 4) 2· 0.5H 2O regenerates the starting material. Recrystallizations from CH 3CN or CH 3NO 2 produce [Co(CNR) 5](ClO 4) 2·0.5H 2O (concentrated solution) or no recovered product (dilute solution). Solid-state properties of magnetic susceptibilities, diffuse reflectance electronic spectra, and mull-infrared are investigated. Distorted square planar coordination of RNC in [Co(CNR) 4](ClO 4) 2 is suggested. Infrared v(ClO 4) strongly suggests monodentate ClO 4 − coordination in [Co(CNR) 4](ClO 4) 2, or [Co(CNR) 4(ClO 4) 2], while the possibility of weaker ClO 4 − coordination in [Co(CNR) 5](ClO 4) 2·0.5H 2O is ambiguous. Isolation of [Co(CNR) 4](ClO 4) 2 is the first observed incident of significant difference between BF 4 − and ClO 4 − salts of Co(II)-arylisocyanide complexes.